- Add cache_utils.py with JSON caching for Google Sheets
- Authenticate and cache Drive/Sheets API services globally to reuse tokens
- Use CACHE_SHEET_MAP dict to resolve cache names securely to Sheet IDs
- Change app.py data fetching to skip downloads if modifiedTime matches cache
- Replace global socket timeout with httplib2 to fix Werkzeug timeouts
- Add VS Code attach debugpy configurations to launch.json and Makefile
